Area Forecast Discussion
Issued by NWS Jackson, KY

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000 FXUS63 KJKL 221841 AFDJKL AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE JACKSON KY 241 PM EDT TUE JUL 22 2014 .UPDATE... ISSUED AT 1107 AM EDT TUE JUL 22 2014 THE GRIDS...ZFP...AND HWO WERE UPDATED MAINLY TO REMOVE MORNING FOG FROM THE FORECAST. THE REGION WILL REMAIN IN BETWEEN AN UPPER LOW MEANDERING ACROSS THE SOUTHEAST AND A SHORTWAVE AND DEVELOPING TROUGH OVER SOUTHERN CANADA AND THE GREAT LAKES REGION. THIS PUT THE AREA JUST TO THE SOUTH AND EAST OF A RIDGE AXIS EXTENDING FROM THE ROCKIES EAST INTO THE OH VALLEY REGION. THIS LEAVES THE AREA UNDER WEAK STEERING FLOW AND SHEAR AND LITTLE OR NO UPPER LEVEL SUPPORT FOR FORCING THROUGH THIS EVENING. THE LATEST GFS AND NAM FORECAST SOUNDINGS HAVE MID LEVEL WARM AIR AND KEEPS THE ATMOSPHERE CAPPED AT JKL THROUGH THIS EVENING. NEAR LOZ...THERE IS A BIT WEAKER CAPPING IN BOTH MODELS...BUT AT BOTH LOCATIONS THE 6Z AND 12Z NAM HAVE THE STRONGER CAP. SOME SHALLOW SHOWERS OR SPRINKLES MAY STILL OCCUR ACROSS THE NORTHWEST TWO THIRDS OF THE AREA...BUT THUNDER CHANCES APPEAR VERY LOW. THE 12Z NAM FORECAST SOUNDINGS INDICATE A WEAKER CAP IN THE TIER OR TWO OF COUNTIES ALONG THE TN AND VA BORDER FROM MCCREARY NORTH AND EAST TO PIKE COUNTY. CONVECTION APPEARS MORE PROBABLE IN THIS AREA...BUT COVERAGE IN ALL AREAS MAY AGAIN BE LIMITED IN COVERAGE SIMILAR TO YESTERDAY. WE WILL CONTINUE TO EVALUATE TRENDS AND CU FOR POSSIBLE LOWERING OF POPS INTO THIS EVENING. UPDATE ISSUED AT 745 AM EDT TUE JUL 22 2014 SOME OF THE DEEPER VALLEYS HAVE SOME DENSE FOG THAT HAS DEVELOPED OVERNIGHT AND IS NOW STARTING TO LIFT A BIT. LOW TEMPERATURES HAVE DROPPED INTO THE UPPER 60S TO AROUND 70 IN MOST PLACES. HAVE UPDATED TO INPUT THE LATEST OBS INTO THE GRIDS. THE REST OF THE FORECAST IS GOOD TO GO. HAVE SENT THE GRIDS TO NDFD AND THE WEB SERVERS. && .SHORT TERM...
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(TODAY THROUGH WEDNESDAY) ISSUED AT 348 AM EDT TUE JUL 22 2014 CURRENT CONDITIONS ACROSS EASTERN KENTUCKY FEATURES SOME DISSIPATING CLOUD COVER AS SOME UPPER LEVEL RIDGING IS NUDGING INTO THE AREA FROM THE HEIGHT CENTER OVER THE SOUTH CENTRAL PLAINS. WITH THIS DISSIPATION...SOME FOG WILL DEVELOP IN THE VALLEYS TOWARDS DAWN. WILL ADJUST TEMPERATURES A BIT AS WELL TO ADDRESS THE LOW TEMPS IN THE MORE SHELTERED VALLEYS. HEADING INTO THE DAY...THE MENTIONED RIDGE AND WARMER MID LEVEL TEMPS INTO THE MID LEVELS WILL IMPACT THE AIR MASS OVER EASTERN KENTUCKY. THIS WILL IMPEDE CONVECTION AGAIN TODAY BUT MAINLY IN THE NORTHWESTERN COUNTIES. MODELS HAVE UNDERESTIMATED THE STRENGTH OF THE RIDGE AXIS NUDGING INTO THE AREA ON MONDAY BUT RECENT RUNS LOOK TO HAVE HANDLED THIS SCENARIO BETTER. WILL GO WITH AERIAL COVERAGE AGAIN BUT WITH MAINLY ISOLATED COVERAGE NORTHWEST TO SCATTERED IN THE SOUTHEAST ALONG THE MOUNTAINOUS COUNTIES. HEADING INTO WEDNESDAY...THE STRONG SHORTWAVE MOVING INTO THE GREAT LAKES REGION AND LOWER OH VALLEY WILL PUSH THROUGH. THIS MAY BE SCENARIO MAY BE ANOTHER EXAMPLE OF THE ENERGY GOING THROUGH THE BASE OF THE TROUGH AND BECOMES CUT OFF FROM THE MID LEVEL RIDGES OVER THE SOUTHERN CONUS. NONETHELESS...WILL GO WITH NUMEROUS COVERAGE INTO WEDNESDAY AS THE FRONT APPROACHES AND SOUTHWEST FLOW INCREASES. PLENTY OF INSTABILITY LOOKS TO BE PRESENT WITH THIS SET UP WITH CAPE VALUES GETTING INTO THE 2500 J/KG RANGE AND WHILE THE CAP STILL LOOKS TO BE PRESENT...THE FORCING AVAILABLE SHOULD BE ENOUGH TO OVERCOME IT. THIS AND SPC HAS ASSIGNED A 5% SEVERE THREAT FOR THE NORTHWESTERN COUNTIES. THOUGH WITH THE SLIGHT INCREASE STEERING FLOW...MAY NEED TO TAKE THE DURATION OVER AN AREA CONCERN. SHEAR LOOKS TO BE WEAK AS WELL FOR THIS SET UP SO ANY SEVERE CONCERN WOULD BE ISOLATED FOR COLLAPSING CELLS WITH NO ORGANIZATION. WILL GO WITH HIGH POPS THROUGH WEDNESDAY WITH NO SEVERE MENTION BUT WITH SOME LOCALLY HEAVY RAINFALL POSSIBLE. SLIGHTLY ABOVE NORMAL TEMPS AND DEW POINTS CLIMBING INTO THE LOW 70S LOOK TOP BE THE CASE THROUGH THE SHORT TERM. .LONG TERM...(THURSDAY THROUGH TUESDAY) ISSUED AT 241 PM EDT TUE JUL 22 2014 FORECAST WILL START OFF DOMINATED BY A STRONG RIDGING PATTERN OVER THE SOUTHWEST CONUS...AND STRONG CLOSED LOW OVER EASTERN CANADA. THIS WILL PLACE EASTERN KY IN A TROUGHING PATTERN WITH FALLING HEIGHTS AND A SERIES OF SHORTWAVES UNDER GENERALLY NW FLOW. THE FIRST OF THESE SHORTWAVES WILL BE EXITING THE REGION AT THE BEGINNING OF THE FORECAST PERIOD...WITH MOISTURE AND PRECIP CHANCES COMING TO AN END DURING THE DAY THURSDAY FROM NW TO SE AS DRIER MORE STABLE AIR FILTERS IN FROM THE NORTH. THIS BRIEF AREA OF HIGH PRESSURE WILL KEEP DRY AND COOLER CONDITIONS FROM THURSDAY EVENING THROUGH FRIDAY NIGHT. HIGHS WILL REACH AROUND 80 OR SLIGHTLY BELOW BOTH OF THESE DAYS. UPPER LEVEL HEIGHTS WILL BRIEFLY CLIMB FRIDAY INTO SATURDAY...AS THIS HIGH PRESSURE SITS OVERHEAD. HOWEVER...BY SUNDAY HEIGHTS WILL BEGIN FALLING ONCE MORE AS ANOTHER SHORTWAVE BEGINS ITS DECENT ON EASTERN KY. MEANWHILE...AT THE SURFACE...A FRONTAL BOUNDARY WILL SET UP ACROSS KY DURING THE DAY SATURDAY AND INTO SUNDAY. THE SHORTWAVE...IN CONJUNCTION WITH THE BOUNDARY...WILL CREATE YET ANOTHER GOOD CHANCE OF CONVECTION SATURDAY AFTERNOON...NIGHT...AND THROUGH THE DAY SUNDAY. WARM MOIST AIR WILL FLOW IN AHEAD OF THIS FRONTAL BOUNDARY...ALLOWING TEMPS TO RISE BACK INTO THE MID 80S WITH HIGH HUMIDITY ON SATURDAY. A COOLER AIRMASS BEHIND THE FRONT WILL DROP TEMPS BACK DOWN SLIGHTLY TO THE LOW 80S BY SUNDAY. THE UPPER LEVEL TROUGH WILL DESCEND SOUTHWARD INTO THE CONUS BY THE END OF THE PERIOD...WITH SHOWERS AND THUNDERSTORMS EXPECTED TO CONTINUE BOTH MONDAY AND TUESDAY. HOWEVER...EXPECT THIS DESCENT TO ALSO BRING WITH IT A MUCH COOLER AIRMASS...WITH HIGHS EVENTUALLY DROPPING INTO THE UPPER 70S BY THE END OF THE FORECAST PERIOD ON TUESDAY. OVERALL MODELS HAVE A FAIRLY GOOD HANDLE/AGREEMENT DURING THE MID TERM WITH THE EXITING OF THE COLD FRONT AND ASSOCIATED PRECIP. HOWEVER...FOR THE SYSTEM MOVING IN DURING THE WEEKEND...THE ECMWF SEEMS TO TAKE THE FASTEST TRACK BRINGING WIDESPREAD PRECIP TO MUCH OF EASTERN KY BY 12Z SATURDAY...WHILE THE GEM AND GFS ARE JUST PULLING IT NEAR THE KY STATE LINE NEAR THIS TIME. THE GFS IS BY FAR THE SLOWEST OF THE SOLUTIONS...SO ALLBLEND RUN SEEMED TO STICK CLOSER TO THE ECMWF SOLUTION AS FAR AS POPS WITH THE LACK OF PRECIP IN THE GFS. DROPPED DOWN CHANCES SLIGHTLY TO COUNTERACT THE STRONG PULL TOWARDS THE ECMWF AND MATCH UP BETTER WITH SURROUNDING OFFICES...BUT OVERALL CONFIDENCE IS FAIRLY LOW WITH THE LACK IN CONTINUITY BETWEEN THE MODELS. LUCKILY...ALL THE MODELS DO KEEP THE PRECIP OVER US BOTH MONDAY AND TUESDAY...SO CONFIDENCE IS FAIRLY HIGH THERE. BASED ON THE UNCERTAINTY FOR SATURDAY...WILL STICK TO THE ALLBLEND SOLUTION AND TRY TO MATCH WITH NEIGHBORING OFFICES.
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&& .AVIATION...(FOR THE 12Z TAFS THROUGH 12Z WEDNESDAY MORNING) ISSUED AT 745 AM EDT TUE JUL 22 2014 PATCHY FOG WILL DISSIPATE WITHIN THE NEXT FEW HOURS ACROSS THE AREA. CU WILL BEGIN TO DEVELOP EARLY TODAY WITH SOME ISOLATED TO SCATTERED SHOWERS AND STORMS DEVELOPING. THE MAIN BULK OF THE ACTIVITY WILL BE TO THE EAST WITH ISOLATED ACTIVITY ELSEWHERE SO WILL GO WITH OUT THUNDER AT THE TAF SITES. TONIGHT WILL SEE MORE FOG DEVELOPMENT AS SOUTHWEST FLOW FINALLY SETS UP AHEAD OF AN APPROACHING COLD FRONT. ALL THUNDERSTORM ACTIVITY ASSOCIATED WITH THE FRONT SHOULD HOLD OFF TILL AFTER 12Z. WINDS WILL BE LIGHT THROUGH THE PERIOD. && .JKL WATCHES/WARNINGS/ADVISORIES... NONE. && $$ UPDATE...JP SHORT TERM...SHALLENBERGER LONG TERM...JMW AVIATION...SHALLENBERGER

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